Virtually no single event can cause as much destruction or engender a feeling of terror in an individual than can a fire. Many alarm systems have been developed and are currently on the market which provide both an alarm system for alerting the individuals present in a particular building or similar structure of the presence of a fire, and then communicating this information to the proper authorities, such as the fire department and the police department. However, these systems are often time prohibitively expensive to the average home owner or they do nothing to alleviate the potential damage which can be caused by the fire.
One potential danger which can occur, and can substantially increase the potential for physical harm to people and increase the damage to various structures, is for the fire to spread to the electrical wiring system which is provided within the structure. Although this system is, of course, important to providing energy to the many electrical appliances and other devices which are utilized, it can also be the cause of increased damage to the structure once a fire is burning. Therefore, it is important that a system which is inexpensive to opeate, which alerts an individual to the presence of a fire condition, and which prevents current from flowing through existing electrical wiring system if a fire condition is sensed, be developed.
The prior art is replete with various devices which employ the existing electrical wiring in buildings to both provide an alarm and to disable the electrical system when a fire is sensed. One such device is described in U.S. Pat. No. 3,872,355 issued to Klein et al. This patent shows a fire protection system used in connection with a ground fault circuit interrupter (GFCI). This patent employs a thermal sensor which is incorporated into an electrical outlet. This sensor senses the presence of a thermal condition above an appropriate temperature threshold and either activates the GFCI unit which interrupts the current in the circuit, or simply activates an alarm at the amain circuit breaker without interrupting the circuit. Although the patent to Klein et al utilizes the existing electrical circuitry in a building for interrupting the current flow in the wiring and additionally activating an alarm, various problems have been found to exist with this particular device.
U.S. Pat. No. Re. 31,147 issued to Helwig, Jr. et al discloses a ground fault and fire detector system which detects the presence of a ground fault current or a fire and opens a circuit breaker to disconnect the power lines from the electrical equipment to which they are connected. However, it should be noted that the particular fire sensor which is utilized is not directly provided in an electrical outlet or wall switch.
U.S. Pat. No. 3,644,912, issued to Allen, Jr. discloses a sensing unit that operates an alarm when it detects a current flow through the ground wire. It should be noted that this patent discusses a system in which a removable sensing means is provided and one which does not operate to interrupt current through the system.
U.S. Pat. No. 3,320,601 issued to Yankus discusses a fire sensing alarm in combination with electric power receptacles which indicate the presence of a fire by an energizing fire alerting alarm connected to a thermally sensitive bimetallic disc provided at the receptacle. As was true with respect to the patent to Allen, Jr., this patent does not interrupt the current flow in the electrical wiring system when a fire is detected.